When Luis Robert laced a walk-off single down the left field line of Friday’s 2-1 win over the Marlins, the White Sox had won six of seven and climbed within 3.5 games of the AL Central lead.

Two bullpen meltdowns later, and reality has reared its head.

“It hurts,” manager Pedro Grifol said after Keynan Middleon and Kendall Graveman combined to give up five runs between the eighth and ninth innings of Sunday’s 6-5 loss. “It’s just one of those days. We’ve got to flush this one.”

Unfortunately, when your record is 29-38, there tend to be more of those days than not.

On Sunday, the White Sox built a 5-1 lead with two-out rallies in the sixth and seventh innings thanks to RBI doubles by Jake Burger and Romy Gonzalez, then a two-run shot by Robert. They were poised for their third consecutive series win ahead of a West Coast trip that stops in Los Angeles and Seattle.

But for the second day in a row, the bullpen faltered. Cruel, as that crew had been lights out for some time — particularly Middleton and Graveman, who entered Sunday with scoreless appearances streaks of 14 and 16, respectively.

Middleton allowed solo home runs to Jorge Soler and Garrett Cooper in the eighth. Graveman conceded another to Jean Segura to lead off the ninth. Then Miami pieced together an additional two runs by way of a catcher’s interference, walk, and two-out, two-run double up the third base line by Bryan De La Cruz.

Graveman declined to use this being his third appearance in four days as an excuse. Hitters were 3-for-50 against him during his streak.

“I didn’t execute,” he said. “I knew the pitches to throw. I’ll give you as much effort as humanly possible, and today I just didn’t think I executed as well.”

Added Grifol: “We put ourselves in a position to win that ballgame today, and the right guys were on the mound, and it didn’t happen. I would not hesitate again to do it the same way on Tuesday.”

But add it to the Marlins’ five-run ninth inning in Saturday’s defeat, and this group is heading West with a bitter taste after last week’s strides.

Gi-oh, yes!

At least the starters continue to shine.

Lucas Giolito built on his six inning no-hit bid at Yankee Stadium last time out by striking out eight over seven innings of one-run ball against the Marlins. The only blemish was a 410-foot blast off the bat of Soler.

“Definitely didn’t have my best stuff,” Giolito said. “But we were able to sequence well and locate well and navigate through the lineup.”

For a time, Giolito appeared poised to pick up his third consecutive win. But the Marlins’ late rally handed him an undeserved no-decision.

This and that

• Tim Anderson was not in the lineup in what Grifol said was a regular off day. The White Sox’ shortstop is slashing .263/.300/.311 for the season and has not homered since last July. But Grifol is betting on a resurgence. “I don’t know how he’s going to end up. My money’s on him, though,” Grifol said. “I know he’s going to figure some things out and end up being the guy he’s always been. He’s been a model for consistency at the top of the order, and he’ll be that again.”
• Yoan Moncada was slated to rest on Sunday as well as he manages a nagging back issue, but Grifol relayed that the third baseman insisted on playing. Batting second in the order, he struck out four times in four at-bats.
• “It’s the back. It’s inconsistent, it’s got a mind of his own. You feel great sometimes, you don’t feel great other times,” Grifol said. “He wants to play. I’m proud of him for that.”